Method of preparing ceramics from polymers derived from cyclic silazanes, and halosilanes

Abstract

This invention deals with new and novel polysilazane polymers, a method for their preparation, and the ceramic materials prepared thereby. An example of such a material is one which is prepared by the reaction of HSiCl 3 and {(CH 3 ) 2 SiNH} x .

That which is claimed is: 
     
       1. A method of preparing a ceramic material, the method comprising pyrolyzing a preceramic polymer in an inert atmosphere or in a vacuum, to a temperature of at least 750° C., until the preceramic polymer is ceramified and a ceramic material obtained, the preceramic polymer consisting essentially of a polymer prepared by contacting and reacting in an inert, essentially anhydrous atmosphere, a component selected from the group consisting of halogen-containing monosilanes having the general formula   R'SiX3     and mixtures of halogen-containing monosilanes having the general formula     R.sub.c 'SiX.sub.(4-c)     wherein c has a value of 1 or 2 and in the mixtures, the number of monosilanes having diorgano-substituted silicon atoms does not exceed the number of monosilanes having monoorgano-substituted silicon atoms, with a cyclic silazane or a mixture of cyclic silazanes selected from the group consisting of silazanes having the general formula (i) (CH 3  R"SiNH) x  and (ii) (C 6  H 5  R"SiNH) x  at a temperature in the range of 0° C. to 260° C. and removing by-produced volatile products by distillation, wherein R' and R" are each independently selected from the group consisting of hydrogen, vinyl, phenyl and alkyl radicals containing 1 to 3 carbon atoms; x has a value of 3 to 6 and X is a halogen atom.   
     
     
       2. A method as claimed in claim 1 wherein the halogen-containing monosilane is HSiCl 3  and the cyclic silazane is {(CH 3 ) 2  SiNH} x . 
     
     
       3. A method as claimed in claim 1 wherein the halogen-containing monosilane is HSiCl 3  and the cyclic silazanes are a mixture of {(CH 3 ) 2  SiNH} 4  and {(CH 3 ) 2  SiNH} 3 . 
     
     
       4. A method as claimed in claim 1 wherein the halogen-containing monosilane is CH 3  SiCl 3  and the cyclic silazane is {(CH 3 )HSiNH} x . 
     
     
       5. A method as claimed in claim 1 wherein the preceramic polymer is further treated with ammonia in an inert, essentially anhydrous atmosphere.